1. Field of the Invention
This invention relates to improvements in a focus detecting apparatus for detecting the focus state from the relative positional relation between two images of an object.
2. Related Background Art
As one type of focus detecting apparatus for a camera, there is known the so-called "image deviation type" in which the exit pupil of the phototaking lens is divided and the relative positional displacement of a pair of images formed by light beams passed through the pupil areas is observed to thereby discriminate the in-focus state.
The signal processing methods for detecting the amount of image deviation from the image signals are disclosed in Japanese Laid-Open Patent Application No. 142306/1983 and U.S. Pat. No. 4,333,007. In these methods, all signals output from sensor rows are used to carry out the focus detecting process. However, the length of the sensor rows in the row direction is considerably great on the viewfinder, and when for example, a deep object to be photographed is seen, it often happens that the amounts of non-in-focus (the amounts of defocus) of various portions differ from one another and the amount of deviation of the image differs between the right-hand portion and the left-hand portion of the output signals of the sensor rows, and if the focus detecting process is carried out by the use of all such output signals, the intermediate focus between the right-hand focus and the left-hand focus will be detected. To cope with such a problem, some of the output signals of the sensor rows may be used to carry out the focus detecting process, but if this is done, there will occur an inconvenience that when the amount of image deviation of the signals is great, that is, when the amount of non-in-focus is great, the amount of image deviation cannot be properly detected. Related art concerning the amount of defocus is disclosed in U.S. Ser. No. 936,746.